On 21.07.2024 11:02, Julien Grall wrote: > Hi, > > On 12/07/2024 17:22, Oleksii Kurochko wrote: >> At least, between Arm and RISC-V most of the code related to Xen page >> table handling are common. >> >> This GENERIC_PT code is based on Arm's arm/mmu/pt.c except some minor >> changes such as introduction of the following functions: >> * get_root_page() >> * xen_pt_check_contig() >> * set_pte_table_bit() >> * sanity_arch_specific_pte_checks() >> * get_contig_bit() >> * set_pte_permissions() >> * flush_xen_tlb_range_va() >> It was done because not every functions has the generic pte_flags and >> it could be a different positions of the PTE bits in a PTE. > While I am always in favor of trying to avoid code duplication, I am not > sure the page-tables are one that should be. > > For instance, you don't have the concept of contiguous page in RISC-V (I > see you introduce dummy flags, but IMHO this is a bit of a hack). All > the code was also written in a way to avoid temporary conflict mappings. > This is to avoid using Break-Before-Make. But on newer hardware this > could be relaxed. > > I am interested to know what the others thinks.
I share the concern; I was rather surprised to see the title, but - not having had the time to look at the patch yet - was kind of guessing (hoping) it wasn't really what the title said. Page table handling quite likely wants to remain arch-specific. Jan
